This invention relates to a cassette attachable to feeder of a printer, copying machine, or like image forming apparatus.
A cassette for use in an image forming apparatus such as a printer and a copying machine is provided with a pair of upright side plates which are provided at opposite lateral ends of a sheet holding plate and are slidable in a direction perpendicular to a sheet feeding direction (hereinafter referred to as a lateral direction). By moving these side plates up to positions where these plates are in contact with left and right lateral edges of sheets contained in the cassette, cut sheets of A4 size, B5 size, or the like, and various envelopes of specified sizes and unspecified sizes are allowed to be aligned and contained on the sheet holding plate. When this cassette is attached to the feeder of the image forming apparatus, the sheets contained in the cassette are lifted by an upward biasing force given from the sheet holding plate, thereby being brought into pressing contact with a feed roller. The sheets are fed by rotation of the feed roller.
Sheet pressing members are provided at opposite front ends of the cassette so as to hold a leading edge of an uppermost sheet. The sheet pressing members are slidable in the lateral direction integrally with the side plates. Thereby, the sheets are prevented from floating. The pair of side plates restrict the transport of sheets in the lateral direction, thereby preventing an oblique feeding of sheet.
Since the side plates are required to be in contact with the corresponding lateral edges of the uppermost sheet reliably, an upper end of each side plate is located above a lower end of a circumferential surface of the feed roller when the cassette is attached to the feeder of the image forming apparatus. Further, since the sheet pressing members press the uppermost sheet, an upper end of each sheet pressing member is also located above the lower end of the circumferential surface of the feed roller.
Thus, particularly in the case where the side plates and the sheet pressing members are moved laterally inward of the cassette so as to contain sheets of narrow width such as envelopes in the cassette, the side plates and the sheet pressing members strike against the feed roller when the cassette is attached or detached to or from the image forming apparatus. This causes the inconvenience that the feed roller, the side plates, and the sheet pressing members are deformed or damaged. In view of the above inconvenience, it can be considered to arrange the feed roller within the width of the smallest possible sheet contained in the cassette. However, if the feed roller is arranged near the lateral center of the cassette, it becomes difficult to feed the large size sheets properly.
On the other hand, in the case where envelopes formed into a flat container by folding the sheet are contained in the cassette, corners of some of the envelopes project outward from the lateral sides thereof. Accordingly, there outward projecting corners are brought into pressing contact with the side plates, which becomes a load against the upward biasing force given from the sheet holding plate and the envelopes cannot be lifted properly. As a result, the envelopes cannot be brought into pressing contact with the feed roller properly, and the envelopes cannot be transported.